Pen



FIG. 1 is a rear right perspective view of a pen showing my new design;

FIG. 2 is a front left perspective view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a rear elevation view thereof;

FIG. 6 is a left side view thereof;

FIG. 7 is a front elevation view thereof; and,

FIG. 8 is a right side view thereof.

The ornamental design for a pen, as shown and described.